Motion capture is a method of capturing the movement of physical objects. A popular application of motion capture is for capture of movement of physical objects and translation of the movement to an illustration of movement of an animated object.
The process of capturing and translating movement of a physical actor to a corresponding actor in a virtual or animated space can reduce the costs associated with animation. Additionally, translating captured physical movement to an animated space can impart realism to the movements of the animated actor that may not by fully realized when a manual animation process is utilized to create the movements in the virtual environment.
In a typical motion capture system, several motion capture markers are placed on a physical actor. The motion capture markers can be placed, for example, near the joints of the skeletal frame of the physical actor. At least one motion picture camera, and typically several motion picture cameras, is used to capture the movement of the actor and corresponding motion capture markers to a series of picture frames. The position of the motion capture markers can be translated to a skeletal or wire frame having corresponding modeled markers.
The placement of numerous motion capture markers on a physical actor typically does not present a problem if the space of the physical actor is large relative to the number and placement of motion capture markers. The placement of motion capture markers on a physical actor becomes more problematic as the area for markers decreases.
Using the placement of many motion capture markers to capture physical movement can perform well for relatively large spatial displacement of the motion capture markers relative to the marker size, or where errors in motion capture do not substantially affect the resultant animation. Conventional motion capture can work satisfactorily for capturing gross physical movements, such as skeletal movements.
However, in applications such as facial animation, the physical area over which the motion capture markers are to be placed is small. The complexity of facial expression magnifies the number of motion capture markers needed for a conventional motion capture implementation, but increasing the number of motion capture markers positioned on a face of a physical actor may impede the very facial expression that is sought to be captured.
Furthermore, small variations in motion capture markers may equate to large differences in the expression conveyed by the actor. Noise and errors in the motion capture process are effectively amplified in the virtual environment due to the small physical area of the physical actor having the markers and the small changes in motion capture markers corresponding to large changes in facial expression.
Facial animation based on motion capture is desirable to reduce the costs associated with facial animation. It is desirable to reduce the number of motion capture markers placed on the physical actor while simultaneously maintaining the complexity of facial expressions that can be animated from motion capture.